Acne is a common skin condition that causes spots and oily skin. Many articles about acne use confusing language. In this article, we clarify some of these unfamiliar terms.

There are various types of acne, each with different symptoms and severity levels. It usually appears on the face, shoulders, chest, back, or buttocks.

When reading about acne, people may come across lots of unfamiliar terms, and some people may find them confusing.

This guide offers 40 definitions to help.

Acne: This is the general name for a common skin condition that causes spots and oily skin. Acne can involve various skin blemishes, including:

  • blackheads
  • whiteheads
  • papules
  • pustules
  • cysts
  • nodules

Acne vulgaris: This is the medical term for common acne, which distinguishes it from less common forms of acne, such as cystic and nodulocystic acne.

Androgens: These are a type of hormone that stimulate the oil glands and hair follicles in the skin, which can lead to acne. Stress causes increased androgen levels, which is why stress can cause acne breakouts.

Antibiotics: Drugs that treat infections caused by bacteria and other microorganisms. Doctors may prescribe antibiotics to treat bacterial overgrowth related to acne.

Bacteria: These are single-celled microorganisms. An overgrowth of bacteria within the follicle may cause inflammation, leading to acne.

Blackhead: A noninflammatory comedo with firmly packed contents and a dark-tipped plug. Also called an open comedo.

Chemical peel: This procedure involves applying a type of organic acid, most commonly salicylic, glycolic, or lactic acid, to the skin to remove dead cells. Dermatologists use chemical peels to treat two types of acne — blackheads, and papules. Many people will experience mild burning and stinging.

Closed comedo: See whitehead.

Comedo: An acne lesion. A comedo is a clogged hair follicle or pore in the skin. A comedo occurs when debris, called keratin, combines with oil to block the pore. A blackhead is an open comedo, and a whitehead is a closed comedo. The plural of comedo is comedones.

Cysts: Deep, painful, pus-filled lesions that can cause scarring. Cysts occur in people with severe acne. If large cysts do not respond to medicine, a doctor may need to excise and drain them.

Cystic acne: A severe form of acne where the person develops multiple cysts. Antibiotics, hormonal medicines, and isotretinoin may help treat cystic acne.

Dermabrasion: A medical procedure that involves the controlled abrasion, or wearing away, of the upper layers of the skin with sandpaper or another mechanical means to unplug pores. It can make acne scars smoother and less visible.

Exfoliation: This is a mechanical or chemical method of peeling off the top layer of the skin at a microscopic level to unblock clogged pores.

Hair follicle: A small cavity in the skin from where a hair grows and into which the oil glands open. Cells that derive from the outside, or epidermal, layer of the skin line the follicle.

Hormonal treatments: Although many people with hormonal acne have normal blood hormone levels, fluctuations in the levels can impact the skin. Doctors may prescribe birth control pills and spironolactone to people with normal hormone levels.

Hormone: A chemical substance produced in the body that controls and regulates the activity of specific cells or organs. Certain hormones contribute to acne.

Infection: The invasion of the body by a harmful bacterium or another organism. Skin infections can occur when a person pops or scratches an acne lesion because bacteria can enter through broken skin.

Inflammatory: Inflammatory acne causes inflamed lesions. Symptoms include skin warmth, swelling, and pain, and discoloration of the skin. Inflammation is the body’s natural protective response to injury or infection.

Isotretinoin: This is a systemic medication that doctors prescribe to treat severe or cystic acne that involves deep, painful cysts, and nodules. Females of childbearing age should take special care with this drug due to potential links with congenital disabilities.

Laser therapy: Laser and other light therapies reduce the Propionibacterium acnes (P. acnes) bacteria that may cause acne.

Lesion: A physical change in body tissue caused by disease or injury. An infection of the sebaceous follicle causes a physical change in the skin. leading to acne lesions.

Nodules: Cysts that contain a large amount of pus or bacteria. This form of acne typically causes pain and extends deeper into the skin layers.

Nodulocystic acne: A severe form of acne characterized by multiple inflamed and uninflamed nodules. It usually affects the face, chest, and back, and is more common in males.

Noncomedogenic: A product that does not cause comedones, e.g., a noncomedogenic shampoo.

Open comedo: See blackhead.

Papule: Small, firm lesions that appear on the surface of the skin. They may or may not become infected.

Pimples: Small papules or pustules.

Prescription: A doctor’s order to prepare and administer a drug or device for a person.

Propionibacterium acnes (P. acnes): A natural bacterium on the human skin with links to acne. P. acnes feeds and proliferates in clogged hair follicles where sebum is trapped.

Puberty: The developmental stage between childhood and adulthood. Puberty usually develops in early teens alongside a significant increase in hormone production. Acne is common during puberty due to hormonal changes in the body.

Pustule: An inflamed comedo that resembles a whitehead and is surrounded by a dark or red ring. Skin redness is more prominent on lighter skin and less apparent on people with darker skin.

Rash: An area of skin that contains many small blemishes. People also call this a breakout or eruption.

Rosacea: Doctors may refer to this as adult acne because it occurs mostly in adults. Pimples, discoloration of the skin, and, in advanced stages, thickened skin, characterize this condition.

Sebaceous gland: This is a normal gland of the skin that empties sebum into the hair follicle near the skin’s surface. Sebaceous glands attached to hair follicles are mostly on the face, neck, back, and chest.

Sebum: An oily secretion of the sebaceous gland that helps to preserve the flexibility of the hair and skin.

Severity: Medical professionals categorize acne severity based on the number of lesions a person has:

  • mild acne: <30 lesions
  • moderate acne: 30–125 lesions
  • Severe acne: >125 lesions

Tetracycline: An antibiotic that doctors often prescribe to treat acne. It is effective against a remarkably wide variety of organisms.

Therapy: Acne therapy refers to an individual’s course of treatment, usually decided with a doctor’s help.

Topical: A topical medicine is one that the person applies directly to the affected area of skin. The medication aims to affect only a specific area of skin, though the body may absorb some into the bloodstream.

Whitehead: An acne lesion that forms when oils and skin cells block the opening of a hair follicle. Also called a closed comedo.